Vehicles, such as pickup trucks, have a rear window, or backlite, that is mounted in an opening in the rear body panel of the cab--normally behind the operator's seat. These backlites are provided to the truck manufacturer, or the after-market, as window frame assemblies. The current window frame assemblies that are commercially available generally have either a welded metal frame, usually aluminum, or a rigid plastic frame, both versions of which are sized to fit in the body panel opening.
Irrespective of the material from which it is made, the frame generally has a bow-shaped outline when viewed in elevation, as represented in FIG. 1, with the upper corners being curved to fit the opening in the body panel. The upper portion of the frame thus provides the bow shape, and the lower rail portion, which is generally linear, is secured to the ends of the upper portion. Typically, the upper and lower portions have beveled ends which may be secured together to form the frame. A continuous channel is generally provided along the interior of the frame to support the upper and lower edges of the sliding window pane, or panes. A second, parallel channel supports a pair of fixed window panes.
Such window assemblies normally take the form of: one fixed window and one sliding window; two fixed and two sliding windows; or, two fixed windows and one sliding window. The most popular of these combinations appears to be two fixed windows and one sliding window. The fixed windows are secured in the frame, and the frame is bonded, or otherwise secured, within the opening in the rear wall of the vehicle cab. The sliding window is preferably disposed medially of the two fixed windows, which facilitates operation of the sliding window by either the driver or a passenger.
The side edges of the fixed window panes, adjacent the sliding window pane, are supported by vertical struts which are secured between the upper and lower portions of the frame. The remaining sides of the fixed window panes are each secured to, and are sealed in, the frame. A separate seal is provided along the upper and lower edges of the sliding window pane to prevent leakage of moisture to the interior of the vehicle when they are closed. The general structure incorporated in the frame assemblies for such windows is described in U.S. Pat. No. 5,228,740 issued on Jul. 20, 1993, to Robert B. Saltzman for "Vehicular Window Frame Assembly for Sliding Window Panes" and is owned by Chardon Rubber Company, the assignee of the present invention.
The present invention focuses on the specific seal configuration employed along the closure edge of the sliding pane--i.e.: the leading edge of the sliding pane which delineates one side of the opening provided when the window is open as well as that edge which moves into opposing engagement with a locking flange on the appropriate vertical strut when the window is closed.
With reference to FIG. 1, a representative window frame assembly 10 includes a frame 11, a pair of laterally spaced, first and second, fixed window panes 12 and 13 and a sliding window pane 14 disposed between the fixed panes 12 and 13. The frame 11 is preferably fabricated from an upper bow portion 15 and a lower, or bottom, rail portion 16 which are secured at the bevelled corners 18 and 19 formed at the intersection of the bow portion 15 with the opposite ends of the normally linear rail portion 16.
These window assemblies generally include a seal member affixed to that stationary window pane 13 adjacent the opening to be spanned by the sliding window pane 14. Prior known seal members generally have one or two lip portions which engage the sliding window in an attempt to prevent the incursion of water when the window is closed.
That prior art solution depicted in FIGS. 2 and 3 represents a single lip seal 20 having a mounting base 21 that is received within a supporting recess 22 presented from the fixed, vertical strut 23. The seal 20 has a single lip portion 24 that extends perpendicularly to the plane of the sliding window pane 14 when the seal 20 is unstressed, as depicted in FIG. 2. An annular stress accommodator 25 is interposed between the base 21 and the lip portion 24. The flexibility of the lip portion 24 together with the resilience afforded by the annular stress accommodator 25 permits the lip portion 24 to lie along, or to be otherwise capable of bending in, the direction that the sliding window moves when being closed. The resulting disposition of the seal 20 when the sliding window pane 14 is closed is depicted in FIG. 3. As is well known, and as can be observed from FIG. 2, the single lip portion 24 which engages the sliding window pane 14 is susceptible of being lifted therefrom by external pressure along the window surface.
The external application of pressurized water against a seal having a single lip portion 24 is represented by arrow 26 in FIG. 3. With the pressurized water thus applied against the juncture of the single lip portion 24 against the sliding pane 14, the sealing affect can be readily breached to permit entry of the water between the lip portion 24 of the seal 20 and the sliding window pane 14 to enter the cab of the vehicle. This can occur in a car wash, and it can also occur when a power nozzle is used to clean the vehicle. It should be appreciated that the interaction of the locking catch assembly 28 mounted on the leading edge 29 of the sliding window pane 14 with the locking flange 30 that is also presented from the fixed, vertical strut 23 does not preclude the passage of any water that breaches the integrity of the seal 20.
When only a single lip 24 is utilized experience has shown that it is, therefore, virtually impossible to prevent the entrance of water into the cab. Attempts have been made to fabricate the single lip portion such that it applies a significant sealing force, but such an approach not only makes it more difficult to open and close the sliding window but also increases the cost of the seal.
A second solution to the problem, as seen in FIGS. 4 and 5, has been to provide a two lip seal 35, the mounting base 36 of which is also secured within the supporting recess 22 presented from the stationary, vertical strut 23. The seal 35 has two spaced lip portions 38 and 39 that extend outwardly from a transverse web 39 and toward the locking flange 30 presented from the strut 23. The two lip portions 38 and 39 are thus configured to lie against, and seal, against the sliding window pane 14. As seen in FIG. 4, both lip portions 38 and 39 are disposed to point in the direction that the sliding window pane 14 moves when it is being closed in order to prevent either of the lip portions 38 or 39 on the seal 35 from engaging the leading edge 29 of the sliding window pane 14 and thereby precluding, or interfering with, the ability of the sliding pane to close. This problem is often identified as "seal rollover."
The space 40 between the lip portions 38 and 39 is typically open to atmosphere, as by one or more apertures 41 that are disposed at the lowest point within the window frame assembly 10 (FIG. 1), and at a location that will not effect communication between the space 40 and the interior of the cab. This arrangement is well known to the prior art. Even so, this second arrangement does admit water into the cab when the water originates from a high pressure jet, as represented by the arrow 42 in FIG. 5. It is true that the second type of seal 35 is generally more effective than the single lip seal 20, but it is more expensive and requires a venting arrangement to clear the accumulation of any water that is admitted into the space 40 between the two tip portions 38 and 39. These requirements further add to the cost and complexity of the window assembly.